It is commonly known that sickle cell patients possess red blood cells that have abnormal rheological properties. The cell properties affect bulk vascular flow in general and microvascular flow in particular. Severe manifestations of this disease can be observed acutely, during intensely painful crises, and chronically, as demonstrated by damage to the cardiovascular system and various organs. It is our intention to develop and explore the use of non-invasive instrumentation to study the character and degree of peripheral blood flow in stable sickle cell patients. We are currently using commercial devices to monitor non-invasively several variables. Because the devices we employ are relatively new, we will also develop a reliable means for evaluating them for potential use with our patient population. Flow studies of this nature can lead to improved understanding of the micro-obstructive component of sickle cell disease as well as serve to evaluate potential therapies such as hydroxyurea.